1

Localized Aviation Model Output Statistics Program (LAMP): Improvements to convective forecasts in

response to user feedback

Judy E. Ghirardelli

National Weather ServiceMeteorological Development Laboratory

October 11, 2011

“Friends/Partners in Aviation Weather” ForumNBAA Convention

Las Vegas, NV

LAMP Background• Statistical Guidance of sensible weather

Produced hourly, 25-h forecast period Valid at stations (airports) and on a grid

• Elements of interest to Aviation:• Winds (at stations)• Ceiling height (at stations and gridded)• Visibility (at stations and gridded)• Thunderstorms (at stations and gridded)

Visibility

Thunderstorms

Ceiling Height

2

How Did New LAMP Convection Guidance Evolve ?

• Existing Product: LAMP Lightning (LAMP ltg) Predictand: ≥ 1 Cloud-to-Ground (CTG) lightning strike

• Review of existing practices to verify convection products (ESRL) indicates radar refl. of ≥ 40 dBZ used as indicator of “convection” Problem: the verifying “truth” is not consistent with what LAMP lightning

was intended to forecast• FAA evaluation of operational LAMP ltg probabilities

Lacks spatial detail, skill, and sharpness especially beyond 6 hours • MDL decisions (June 2010)

Define convection predictand: radar ≥ 40 dBZ and/or ≥ 1 CTG lightning strikes

Add NAM MOS (to GFS MOS) convection probabilities as additional model input

3

Thunderstorm (current)

Convection (future)

4

New LAMP Convective Guidance

• Features: Defined from Cloud-to-Ground

(CTG) ltg GFS MOS 3-h thunderstorm

probability predictors 2-h period / 20-km gridboxes 1-h cycle; 3 – 25 h projections Other predictors

• Criticisms: Convection can occur without

CTG lightning Thunderstorm probabilities lack

sharpness

• Features: Defined from CTG ltg / ≥ 40 dBZ

radar reflectivity GFS & NAM MOS 2-h convective

probability predictors 2-h period / 20-km gridboxes 1-h cycle; 3 – 25 h projections Other predictors

• Solution: Convection can be indicated when

there is little or no lightning Convection probabilities exhibit

good sharpness

5

Convection Potential• Four convection potential categories

No, low, medium, and high Each category is defined objectively from a pre-determined

probability threshold Each probability threshold corresponds to a prescribed bias

criterion, where bias is

~ 2.7 = low potential ~ 1.1 = medium potential

(lightning ~ 1.2) ~ 0.4 = high potential

• Convection potential aids interpretation of probabilities with peak values < 100%

6

LAMP Lightning (LTG) vs Convection(CNV) Prob. Skill for 1800 UTC Cycle

Cool season Spring season

Summer season

Independent sampleOct 2009 – Oct 2010

7

LAMP Lightning vs Convection Probability Reliability and Sharpness

New LAMP Convective Guidance

8

August 27, 2011: 1800 UTC cycle, Hurricane Irene

LAMP Lightning LAMP Convection

New LAMP Convective Guidance

9

Convection Probabilities

Convection Potential

August 25, 2011: 1200 UTC cycle, 6-8 hour projection

10

Current LAMPThunderstorm

New LAMPConvection

11

12

Note that this is a 23-hour projection, and the LAMP convective probabilities are about 90% while the LAMP thunderstorm probabilities are about 30%.

13

14

May 26, 2011: 0000 UTC cycle: Chicago, Atlanta, New York all affectedConvective Guidance Examples

15

Convective Guidance ExamplesSeptember 07, 2011: 0000 UTC cycle

16

September 07, 2011: 0000 UTC cycle: 22-24 hour projectionConvective Guidance Examples

Future Work: Additional Products

17

Verification Graphics: overlay probabilities with marker indicating if convection was

observed

Text bulletins at stations: to support

prototype Gate Forecasts

Implementation Plans

• Convection products produced in real time since March 2011 24 cycles per day (not supported 24x7) Web Graphics at:

http://weather.gov/mdl/lamp/compare.php http://weather.gov/mdl/lamp/convection.php

GRIB2 files available at:http://www.mdl.nws.noaa.gov/~glmp/conv_grib/

• Implement on CCS parallel system before March 2012• Available in experimental NDGD March 2012• Transmit grids on SBN/NOAAPORT – planned FY12/13

• Contact: Judy.Ghirardelli@noaa.gov 18